A mold is necessary to manufacture a cast metal. Examples of the mold are a heat-hardening mold, self-hardening mold, and gas-hardening mold. For example, the self-hardening mold is generally manufactured by a method of filling kneaded sand containing a refractory granular material, hardener, and binder in a wooden model or resin model (to be collectively called “a model” hereinafter), and hardening the binder. To manufacture a mold having a complicated shape, however, it is naturally necessary to increase the number of models, and this complicates the process. Also, even when the number of models can be increased, no mold can be manufactured if the models cannot be removed from the mold.
To solve these problems, a mold manufacturing technique using three-dimensional laminating and shaping capable of directly manufacturing a mold without using any model has been proposed. Three-dimensional laminating and shaping is a method of manufacturing a mold by directly using a three-dimensional shape input on a CAD (Computer Aided Design) system as a stereomodel (three-dimensional model).
A known example of this mold manufacturing technique using three-dimensional laminating and shaping is a method (two-component self-hardening mold) of repeating an operation of laminating (recoating) kneaded sand obtained by mixing a refractory granular material and liquid hardener and printing a binder on the kneaded sand based on CAD data, and removing the kneaded sand from an unprinted portion after the binder is hardened (see, e.g., patent literature 1).